The present invention relates to an information storage apparatus including a disk array including a disk drive and a cache (volatile memory), a host, an uninterruptible power supply (UPS) for the disk array, and a UPS for the host and a control method of the same.
In a system configuration of an information storage apparatus including a disk array including a disk drive and a cache, a host, a UPS for the disk array, and a UPS for the host, when a power failure occurs, there is required, there is required a procedure to guarantee user data as follows.
Occurrence of Power Failure
    {circle around (1)} Processing of host termination and cash flush of the disk array (to write data of the cache in the disk drive) and setting of the system to a write-through mode (to inhibit use of the cache).    {circle around (2)} Recognition of completion of host termination    {circle around (3)} Processing of host UPS termination    {circle around (4)} Processing of disk array termination    {circle around (5)} Recognition of completion of disk array termination    {circle around (6)} Processing of termination of disk array UPS.
JP-A-8-297530 describes a technology related to the operations above.
In accordance with the technology of the publication above, only processing on the host side of {circle around (1)} and operations of {circle around (2)} and {circle around (3)} can be automatically accomplished. However, the processing on the disk array side of {circle around (1)} and operations of {circle around (4)} to {circle around (6)} are disadvantageously required to be carried out by human power. That is, when a power failure occurs on the host side, only the termination processing is required to be immediately executed; whereas, on the disk array side, the termination processing is carried out only after data of the host side are entirely received. Therefore, the termination must be achieved after the completion of the host termination is recognized and this restriction results in a difficulty.